The human nose is responsible for warming, humidifying and filtering inspired air. The nose is mainly formed of cartilage, bone, mucous membranes and skin. The right and left nasal cavities extend back to the soft palate, where they merge to form the posterior choanae. The posterior choanae opens into the nasopharynx. The roof of the nose is formed, in part, by a bone known as the cribriform plate. The cribriform plate contains numerous tiny perforations through which sensory nerve fibers extend to the olfactory bulbs. The sensation for smell occurs when inhaled odors contact a small area of mucosa in the superior region of the nose, stimulating the nerve fibers that lead to the olfactory bulbs.
The nasal turbinates are three bony processes that extend inwardly from the lateral walls of the nose and are covered with mucosal tissue. These turbinates serve to increase the interior surface area of the nose and to impart warmth and moisture to air that is inhaled through the nose. The mucosal tissue that covers the turbinates is capable of becoming engorged with blood and swelling or becoming substantially devoid of blood and shrinking, in response to changes in physiologic or environmental conditions. The curved edge of each turbinate defines a passage way known as a meatus. For example, the inferior meatus is a passageway that passes beneath the inferior turbinate. Ducts, knows as the nasolacrimal ducts, drain tears from the eyes into the nose through openings located within the inferior meatus. The middle meatus is a passageway that extends inferior to the middle turbinate. The middle meatus contains the semilunar hiatus, with openings or Ostia leading into the maxillary, frontal, and anterior ethmoid sinuses. The superior meatus is located between the superior and medial turbinates.
The turbinates are autonomically innervated by nerves arising from the Vidian nerve which contains sympathetic and parasympathetic afferents that can modulate the function of the turbinates to either increase (parasympathetic) or decrease (sympathetic) activity of the submucosal layer. The pterygoid canal carries both parasympathetic and sympathetic fibers, namely the vidian nerve, to the sphenopalatine ganglion. Exclusive of the sphenopalatine foramen (SPF) contents, additional posterolateral neurovascular rami project from the sphinopaletine ganglion via multiple individual postganglionic rami to supply the nasal mucosa. The most common locations for these rami are within 1 cm posterosuperior to the horizontal attachment of the inferior turbinate, within 5 mm anteroinferior to this attachment, and the palatine bone via a foramen distinct from the SPF. Also, Blier, et. al showed that interfascicle anastomotic loops in some cases, are associated with at least 3 accessory nerves. Based on Blier et. al work each accessory nerve could be proximally traced directly to the PPG or greater palatine nerve.
Rhinitis is defined as inflammation of the membranes lining the nose, characterized by nasal symptoms, including itching, rhinorrhea, and/or nasal congestion. Chronic Rhinitis affects tens of millions of people in the US and is a leading cause for patients to seek medical care. Medical treatment has been shown to have limited effects for chronic rhinitis sufferers and requires daily medication use or onerous allergy treatments and up to 20% of patients may be refractory.
In addition to the medications turbinate reduction surgery (RF and micro-debridement) both have temporary duration of effect of 1-2 years and can result in complications including mucosal sloughing, acute pain and swelling, overtreatment and bone damage. Additionally, turbinate reduction does not treat the symptom of rhinorrhea. It is thought that parasympathetic effect of the vidian nerve predominates so that, on transecting it, the result is decreased rhinitis and congestion. This pathophysiology has been confirmed as surgical treatment of the vidian nerve has been tried with great success; however, the procedure is invasive, time consuming and potentially can result in dry eyes due to autonomic fibers in the vidian nerve that supply the lacrimal glands.
Golding-Wood, who recommended cutting the parasympathetic nerve fibers in the vidian canal to decrease the parasympathetic tone to the nasal mucosa, introduced a different approach for the treatment of hypersecretion in 1961. Various approaches to the vidian canal were subsequently developed, and the method was widely employed in the 1970s. However, the original technique was abandoned at the beginning of the 1980s because of its irreversible complications such as dry eyes.
Recent studies have shown that selectively interrupting the Post Nasal Nerves (PNN) in patients with chronic rhinitis improves their symptoms while avoiding the morbidities associated with vidian neurectomy.1 The study by Ikeda et. al suggests that the effect of an anticholinergic drug on nasal symptoms resembled that of PNN resection in patients with chronic rhinitis. Based on his study the glandular mucosal acinar cells were significantly reduced after the PNN resection. The reduction in glandular cells may be explained by decreased secretion of the nerve growth factor or epidermal growth factor regulated by acetylcholine, a major neurotransmitter of parasympathetic systems.
Posterior nasal neurectomy, initially developed by Kikawada in 1998 and later modified by Kawamura and Kubo, is an alternative method in which neural bundles are selectively cut or cauterized from the sphenopalatine foramen. Autonomic and sensory nerve fibers that pass through the foramen anatomically branch into the middle and inferior turbinate and are distributed around the mucosal layer of the nose. Therefore, selective neurectomy at this point enables physicians to theoretically avoid surgical complications such as inhibition of lacrimal secretion.